border-1px($color)
	position: relative
	&::after
		position: absolute
		left: 0
		bottom: 0
		width: 100%
		content: ' '
		border-top: 1px solid $color

border-none()
	&::after
		display: none

bg-image($url)
	background-image:  url($url + '@2x.png')
	@media (-webkit-min-device-pixel-ratio: 3),(min-device-pixel-ratio:3)
		background-image: url($url + '@3x.png')